In my twenties I got really sick; lying in bed for 5 days, bleeding from the lower part of my digestive tract: not pretty. . . Delirious days later and ten pounds lighter and I was recovered, except for one problem: I had diarrhea for the subsequent 14 years. . . . Two years ago [2008] I passed out on the toilet on a ski weekend. The emergency room at Bennington Hospital [Vermont] told me it was a stomach flu.
Four weeks later I got cramps at work. I had to lie on the floor until it passed. Then I drove to my doctor’s office, and he told me that I had diverticulitis, and I had to go to the emergency room. I drove myself, and barely made it. I was in agony; I nearly passed out again while they were interviewing me to see if it was “serious”. . . . I had a perforated colon. . . . I spent the next four days in the pre-operative ward, so if it got worse they could cut me open immediately. I lost 10 pounds. Then I started bleeding, and I realized these were all the same symptoms that I had had 14 years before. My blood pressure got so low that the automated blood-pressure machine wouldn’t work . . .
I mentioned to all three of the doctors I saw that I had had constant diarrhea for the last 14 years, since the first attack, and they shrugged. They told me to eat more fiber, and whole wheat, even though that was what I had been eating for the last 20 years. So I avoided surgery, started eating salad with salad dressing (containing industrial seed oils) and lots of whole wheat. . . . But the more salad and whole wheat I ate, the worse it got. I couldn’t understand why. Finally had to have eight inches of my colon removed. The diarrhea continued, so obviously the cause remained.

Then something happened that, before blogging, wasn’t possible:

Someone sent me a post that Stephen Guyenet did about how dental problems were pretty much all due to diet, not genetics, as I’d been told. As someone who’d had a ton of cavities, and 8 teeth pulled, and was determined to spare his daughters the same fate, I found this of interest.
I started reading the blog. 6 months later, I decided to stop eating seed oils, which eliminated my carb cravings, hence no wheat. Two days later, [unexpectedly] my diarrhea stopped. A good bit of trial and error, some accidental, ensued. [I learned that both] wheat and seed oils cause distress, but different types. The two combined can cause me to pass out. If I eat wheat by accident, then eating saturated animal fats (like cream) causes things to settle down.

After 16 years my symptoms are now completely under my control. . . . I read the ingredients on everything. I make a big mistake once every 6-9 months. [Other benefits:] I’m much more resistant to sunburn, for instance, and my vision improved a bit.

So his problems were due to (a) wheat and (b) too much omega-6. His doctors had no idea.
The Mayo Clinic recommends a “diverticulitis diet” that is clear liquids and low-fiber foods. According to the Mayo Clinic, “mild cases of diverticulitis can be treated with rest, changes in your diet and antibiotics. But serious cases of diverticulitis may require surgery.” The Mayo Clinic, it appears, has no idea what causes diverticulitis.
Tuck added:

It really pisses me off when people dismiss this, because it really makes a difference. I had a colleague who was in the hospital for a colon resection for diverticulitis. When he heard my story, he had the hospital put him on a gluten-free diet. Four days later, instead of having surgery as scheduled, he checked out: cured. He’s symptom-free on a gluten-free diet to this day.

In this post a contract artist who calls himself Wolverine gives a long list of life-threatening medical errors that happened to him. I hope that he will eventually add dates so that the rate of error becomes clearer [more: all the errors happened within a 14-month period] but even without them the stories suggest that life-threatening errors are common. (As does the effectiveness of surgical checklists.) Medicine is a job where if you make a mistake only the customer suffers not you. Surely this is why the error rate is so high. Wolverine was operated on by a surgeon who, because of a fatal error, had lost his license to practice in California. He changed states, was hired again, and made the same error on Wolverine.
I learned about this from Tucker Goodrich, who has been corresponding with the author and told me something remarkable:

He’s eating a paleo with raw milk diet. The other transplant patients he knows are all eating the modern American diet and dying of infections; he’s been infection-free for two years.